Method for gluing optical disc substrates together

Abstract

A method for gluing two disc elements together, in particular substrates for digital audio, video or data discs, such as Digital Versatile Discs (DVDs). The disc elements are held essentially horizontally and coaxially with one another so that a gap is formed between the disc elements, after which, in an inner area of the gap, a liquid adhesive is applied in the form of separate strands in the circumferential direction on the facing sides of the disc elements. The disc elements are brought together against one another and made to rotate rapidly in conjunction with the bringing together in order, by the gravitational force of the upper disc element and the capillary force of the adhesive, in association with the centrifugal force on the latter during the rapid rotation, to form a homogeneous and bubble-free adhesive layer of predetermined thickness between the disc elements.

What is claimed is:  
     
       1. Method for gluing two disc elements together, comprising the steps: 
       a) holding the two disc elements ( 10 ,  12 ) essentially horizontally and coaxially with one another in such a manner that a gap is formed between the disc elements;  
       b) applying in an inner area of the gap, a liquid adhesive in the form of at least one strand ( 18 ,  20 ;  18 ′,  20 ′) in a circumferential direction on both facing sides of the two disc elements ( 10 ,  12 ), characterized in that  
       c) applying the adhesive in separate, circular-arc-shaped strands ( 18 ,  20 ;  18 ′,  20 ′) with a same radius of curvature on the facing side surfaces of the disc elements ( 10 ,  12 ) and with a combined height (h 1 +h 2 ) of the adhesive strands which is greater than a height (d) of the gap between the disc elements;  
       d) rotating the disc elements ( 10 ,  12 ) in relation to one another through approximately one revolution after the application of the respective adhesive strand, one end of the adhesive strand on one disc surface being made to come together with one end of the adhesive strand on the other disc surface, after which  
       e) bringing together the disc elements ( 10 ,  12 ) against one another and made to rotate rapidly in conjunction with the bringing together of the disc elements in order, by means of a gravitational force of an upper disc element and a capillary force of the adhesive, in association with a centrifugal force on the latter during the rapid rotation, to form a homogeneous and bubble-free adhesive layer of predetermined thickness between the disc elements.  
     
     
       2. Method according to  claim 1 , characterized in that the adhesive is applied by means of a single nozzle, the two disc elements ( 10 ,  12 ) each being rotated through up to approximately half a revolution in opposite directions. 
     
     
       3. Method according to  claim 1 , characterized in that the adhesive is applied by means of two distinct, diametrically separated nozzles ( 22 ,  24 ), the two disc elements ( 10 ,  12 ) each being rotated through up to approximately half a revolution in the same direction.